|thanks for the quick reply - system details are|
Asus P4C800 motherboard (http://www.ece.umd.edu/courses/enee759h.S2003/references/e1286_p4c800.pdf)
(Replaced in 2007 with identical motherboard sourced off ebay)
CPU pentium 4 2.4 GHz ( replaced 2007)
BIOS is AMi build 08.00.09 14 oct 2004
Jeanster 405w PSU (Installed in 2008)
1GB RAM ( 2x 512MB) replaced in 2009 with 2x 1GB Hynix DDR 400Mhz
Seagate IDE barracude 80 Gbyte hard drive replaced with 200GB SATA ST3120026AS ( installed last few days)
SATA and IDE data cables replaced on motherboard. All unnecessary power sockets have had their cables removed for testing ( eg CPU fan power, HD LED, etc)
temperatures and voltages are;
CPU 32 C
vcore volt 1.55
If I boot from CD and only have the CD running then the machine can brownout while loading "linux gparted". This behaviour is inconsistent though and the only consistent behaviour is the itunes method. But it does suggest to me that it's not the operating system.
Note that the case has two power switches - one on the PSU and one at the front. If I turn off the PSU one the BIOS loses the date settings and gives me " a new CPU has been installed" message.
I'm thinking there might be some BIOS setting that is causing this?